Novel penicillin compounds



United States Patent 3,116,285 NQVEL PENltIt-Llllhl CSll EPQUNDS Walter B. (Ieimer, New London, and Donald C. Hobbs, East Lyme, Coma, assignors to Chas. Pfizer 3; (3a., inc, New York, Nil! a corporation of Delaware No Drawing. Filed May 25, 1960, Ser- No. 31,563 5 Claims. Kill-230.1)

This invention relates to new antibiotic compounds and their salts and, more particularly, to novel 6-aminopenicillanic acid derivatives and their salts which show resistance to penicillinase.

The term penicillin includes a number of acyl derivatives of 6aminopenicillanic acid which diifer only in the nature of the R group and possess the general formula 0 S CH3 ll R--C-N1ICHCH o-crn 0=( 3NoH-o00I-I (I) in which the acyl moiety is derived from a carboxylic acid. The properties of a particular penicillin are determined by the R group. The best known and most widely used penicillins are benzylpenicillin and phenoxymethylpenicillin wherein R (Formula I) represents the benzyland phenoxymethyl-radicals. Both compounds are eifective via both parenteral and oral administration in the treatment of bacterial infections due to gram-positive organisms but are generally ineffective against gram-negative organisms, many of which are resistant to their action, and against penicillinase producing strains of bacteria, such as Bacillus subtilis, Bacillus cereus and various Staphylococci strains. The penicillinases produced by these bacteria antagonize the antibacterial activity of the penicillin compound by hydrolysis of the beta lactam linkage to produce a biologically inactive penicilloic acid. It is a prominent factor in penicillin resistance or" bacteria.

There has now been discovered a series of novel and valuable derivatives of -aminopenicillanic acid, hereinafter referred to as aphenoxy-fl-hydroxyalkyl penicillins and oc-phenylmercapto43-hydroxyalkylpenicillins, and acyl derivatives thereof, which possess significant activ ity against gram positive organisms and which are unexpectedly resistant to the effect of penicillinases and, therefore, of value in the treatment of bacterial infections due to certain penicillinase-producing organisms resistant to the presently available penicillins. The novel compounds of this invention have, in the acid form, the formula:

wherein X is selected from the group consisting of oxygen and sulfur; R is selected from the group consisting of alkyl containing 1 to 5 carbon atoms and hydrogen; and R is selected from the group consisting of hydrogen and acyl radical of a hydrocarbon monocarboxylic acid containing l to 4 carbon atoms. These novel compounds can, by virtue of the asymmetric center or centers present in the side chain, exist in diastereoisomeric forms, and mixtures thereof, derived respectively from the isomeric precursor acids. When the all-precursor acid is used, a mixture of the diastcreoisomers will be produced. When R is other than hydrogen two dissimilar asymmetric carbon atoms are present in the side chain of these novel compounds giving rise to the existence of additional diastereoisomeric forms derived respectively from the corresponding precursor acids. Therefore, included Within the purview of this invention are the various stereosiomeric modifications and mixtures thereof, of the compounds of Formula II above, all of which exhibit substantial therapeutic activity.

Included in the present invention are the pharmaceutically acceptable salts of these novel and valuable penicillins, that is, non-toxic metal salts such as the sodium, calcium and potassium salts, and non-toxic ammonium and substituted ammonium salts, for example, salts of such non-toxic amines as procaine, dibenzylamine, N,N- bis (dehydroabietyl ethylenediamine, N,N-dibenzylethylenediamine, l-ephenamine, N-benzyl-fl-phenethylamine, I nethylPentylamine, 4,4'-dimethylbenzhydrylamine and other amines which have been used to form salts with benzylpenicillin.

In addition to their resistance to penicillinase and their significant antagonism toward organisms resistant to the heretofore available penicillins, the valuable products of this invention also demonstrate antagonism toward grampositive organisms although the activity towards the latter is somewhat lower than that of phenoxymethylpenicillin. The compounds of this invention wherein R is acyl exhibit no activity against the resistant Staphylococci in vitro. The antibacterial spectrum (in vitro) of a-phenoxy-fi-hydroxyethylpenicillin, and ct-phenoxy-fl-acetoxyethylpenicillin versus a number of gram-positive and gram-negative organisms are compared with that of phenoxymethylpenicillin in Table I. All compounds are used as their potassium salts.

TABLE I Antibacterial Spectra of the Potassium Salts of a-Phenoxy- S-Hydroxyethylpenicillin (A), a-Phcnoxy-fl-Acetoxyethylpcnicillin (B) and Phenoxymetlzylpenicillin (C) Microorganism MIC meg/m1. (B) (C) Staphylococcus aureus 0. 0625 0. 19 0.0312 Staphylococcus aureus 37 50 100 100 Slaphylococcus aureus 400. 50 100 100 Streptococcus pyroocues- 0.0078 0. 04 0. 0156 Streptococcus faeculls. 0. 39 1. 56 0. 156 Diplococcus pneumoniaa. 1 56; 0. 78 pr 1. 56 0. 156 Corynebacierium diphtherz'oe 0. 1 pr 0. 39 0.78 Listeria monocylogeues. 0.19 0. 78 6. 25 Bacillus subtilis 0.125 0. 78 0.019 Streptococcus agulacliaa 0. 0312 0. 09 0. 039 Laclobacillus casei 1. 56; 0.78 pi 3.12 1. 56 Bacterium cmmoniagenes 3.12; 1. 56 pi 0. 39 0.039 Acroboctcr aerogenes 25 100 100 Escherichia coli 100 100 Proteus oulgaris 50 100 100 Pseudomonas ceruginosa 100; 50 101 100 100 Salmonella typhoso 50 100 100 Salmonella golliuarum. 100 100 Salmonella pullorum- 50 100 100 Klcbsiella pneumonia 50 100 100 Neisseriu oonorrlweaa 1. 56; 0. 78 pi 1. Hemophilus pertussis. 1. 56 3.12 12. 5 S ligella 807l71i 50 100 Brucclla brouchiseplica. 100 100 100 lvI llleomyces mallci 100 100 100 Vibrio comma 12. 5; 6. 25 pi 25 12. 5 Pasleurclla mullocldo. 0.125 0. 39 0.39 Candida olbicons 100 100 100 Sarci'no luiea 0. 0039 0.02 Mycobacterium 607 100 100 JJycobccterium berolineuse 100 100 100 Streptococcus pyogeucs scrum. 0. 0625 0. 04 Staphylococcus ourcus serum 0. 0.19 Staphylococcus aurcus 0.1% nucleic acid 0. 39

The therapeutic value of these compounds is evident on comparison of their in vivo activity with that of phenoxymethylpenicillin against S. aurcus infections in mice. The P13 values (50% curative or survival dose) for u-phenoxy-fi-hydroxyethylpenicillin (A) oz-phenOXY-B- acetoxyethylpenicillin (B) and phenoxymethylpenicillin (C), as their potassium salts, are given in Table II in terms of mg./kg.

3 TABLE II PD Values of a-Phenoxy-fieHydroxyethy[penicillin (A),

a-Phcnoxy-B-Acezoxyethylpenicillin (B) and Phenoxymethylpenicillz'n (C) Potassium Salts The activity of a-phenoxy-fi-hydroxyethylpenicillin and its acetoxy derivative against the sensitive S. aureus strain number is similar to that of the widely used phenoxymethylpeniciilin. in contrast to phenoxyrnethylpenicillin, however, e-phenoxy-B-hydroxyethylpenicillin is surprisingly effective via oral, and particularly via parenteral, administration in the treatment or" resistant S. anreus infections in animals including man. It should be noted that a-phenoxy-B-aceto-xyethylpeniciilin is also exceedingly antagonistic in -vivo toward sensitive Staphylococci. The remaining compounds of this invention exhibit similar activity and have, therefore, the same utility. The l-a-phenoxy-[i-hydroxyethylpenicillin and l-a-phenoxy-flacetoxyethylpenicillin are more active than are the corresponding d-diastereoisomers. The l-diastereoisomers of the remaining products of this invention are more active than the d-diastereoisomers.

Further indication of the therapeutic value of a-phenoxy-fi-hydroxyethylpenicillin is evident on comparison of its in vitro activity against various antibiotic resistant S. oureus cultures with that of benzylpenicillin. The minimum inhibitory concentrations are reported in Table III in terms of mcg./ml.

TABLE III Antibiotic a-Phenoxy-fl- Benzyl Resistant hydroxy-ethyl- Penicillin S. aureus penicillin 376 25 100 400 12. 5 100 P/r 3. 12 100 M1 12. 5 50 M2 12. 5 100 M12 6. 25 25 M13 12. 5 100 Oral administration of ct-phenoxy-B-hydroxyethylpenicillin, m-phenoxy-B-acetoxyethylpenicillin and phenoxymethylpenicillin to dogs at dosage rates of mg./ kg. of body weight produce the following blood serum levels.

TABLE IV 1 The ratios indicate the number of test animals which show a positive I'GSDOHSC.

Alpha-phenoxy-B-acetoxyethylpenicillin is thus absorbed to a much greater extent than its corresponding hydroxy compound and phenoxymethylpenicillin. This greater absorption, coupled with the previously mentioned in vivo activity of the acetylated product, makes this compound especially valuable for the treatment of a variety of bacterial infections in animals, including man. The

remaining acylated products of this invention demonstrate similar properties.

The novel and valuable compounds of the present 1nvention, are prepared by the reaction of 6-aminopenicillanic acid with (1) the appropriate acid chloride, or (2) the appropriate acid in the presence of a condensing agent, such as a carbodiimide, pentamethyleneketene cyclohexylarnine and ethoxyacetylene. The diastereoisomers or mixtures thereof, of these valuable products are obtained by utilizing the appropriate form, for example the d, lor dl form, of the acid chloride or acid as reactant. The diastereoisomeric mixtures can, of course, be resolved into the individual diastereoisomers by suitable means such as fractional crystallization, selective extraction, or selective precipitation of an insoluble salt of one diastereoisomer in the presence of the other.

They can also be prepared by the method of Sheehan et al., Journal of the American Chemical Society, 81, 3089 (1959), which utilizes the reaction of D-penicillamine and t-butyl phthalirnidomalonaldehydate as starting materials for a series. of reactions. Substitution of the phenoxyacetyl chloride utilized by Sheehan et al., by, for example, a-phenoxy-,8-hydroxypropionyl chloride in tl e reaction sequence produces a-phenoxy-fi-hydroxyethyipenicillin potassium salt.

It is preferred to utilize the reaction of 6-aminopenicillanic acid with the appropriate acid chloride, for example, ot-phenoxy-fi-hydroxyalkanoyl chloride or aaphenoxy-p-acyloxyalkanoyl chloride in the presence of an acid acceptor at a neutral to moderately alkaline pH level, that is, at pH values of from about 6.0 to about 9.0 since this process produces substantial yields of the desired product.

The valuable compounds of this invention wherein R is an acyl group are preferably prepared by reacting the appropriate a-phenoxy-fi-acyloxyalkanoic acid or a-phenylmercapto-fi-acyloxyalkanoic acid or acid chlorides thereof with 6-aminopenicillanic acid as described above. They can also be obtained by acylation of the proper aphenoxy-fl-hydroxyaikylpenicillin or a-phenylmercapto- ,B-hydroxyalkylpenicillin.

The required starting a-phenoxy-,8-hydroxylalkanoio acids and ot-phenylmercapto-fl-hydroxyalkafioic acids are prepared by known methods. Alpha-phenoxy-fi-hydroxy propionic acid, for example, is prepared by the acylat'ion. of an ester of phenoxyacetic acid, such as the ethyl ester, with ethy lformate in the presence of sodium followed by reduction of the thus produced formyl ester to the phydroxyester. Replacement of ethyl :formate by esters of alkanoic acids containing up to six carbon atoms produces the required ot-phenoxy-fl-hydroxy alkanoic acids. The a-phenylmercapto-fi-hydroxyalkanoic acids are pre pared in the same manner from a-phenylmercaptoacetlc acid esters. Acylation of the ,B-hydroxy acids or esters with the appropriate acylating agent produces the corresponding fl-alkanoxyloxy derivatives.

In addition to the a-phenoxy-/3-hydroxyalkylpenicillins and otphenylmercapto-/i'-hydroxyalkylpenicillins described herein, analogous compounds wherein the hydroxy group is further removed from the alpha-substituted carbon of the side chain also possess similar activity. Such activity is observed irrespective of whether the hydroxy group is a primary, secondary or tertiary hydroxy group.

When prepared as described above the novel antibiotics are obtained as the sodium or potassium salts. They are readily converted to the acid form by neutralization with a mineral acid, such as sulfuric or hydrochloric acids, or a suitable ion exchange resin and are recovered by extraction of their aqueous solution with a suitable water immiscible organic solvent.

The acid forms of the novel antibiotics of the present invention are, in turn, easily converted to salts by reaction with a suitable base. Thus, treatment of the desired antibiotic in aqueous solution with ammonium hydroxide produces the ammonium salt. In like manner other salts such as the calcium, magnesium, barium, potassium and sodium, are for-med. In addition, amine salts, such as the procaine, dibenzylamine, N,N-dibenzylethylenediamine, l-ephenamine and N-benzyl-(S-phenethylaminc salts, are prepared by reacting a solution of the desired antibiotic in an aqueous or non-aqueous solvent with the desired amine. Alternatively, the amine salts are prepared in aqueous solution by reaction a metal salt of the desired antibiotic, e.g. the sodium salt, with the desired amine salt, for example, the amine hydrochloride salt.

This invention is further illustrated by the following examples, which are not to be construed as imposing any limitations on the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications and equivalents thereof which readily suggest themselves to those skilled in Penicillin ml. of ether, only the aqueous phase being maintained. The aqueous phase is then extracted with 3 x 50 ml. volumes of n-butanol at pH 2.0 and the combined nbutanol fractions washed once with water. The n-butanol phase is then extracted with 2 x 50 ml. portions of water, sufficient potassium hydroxide (6 N) solution being added to each portion during extraction to produce an aqueous extract of pH 7.0. The combined aqueous extracts are washed with 20 ml. of ether then freeze dried to give a mixture of the potassium salts of dand l-a-phenoxy-5- hydroxyethylpenicillin.

EXAMPLE III The procedure of Example II is repeated but using the appropriate acid in place of a-phenoxy-fi-hydroxypropicnic acid. The convenience only the side chain is listed. In each case a mixture of the stereoisomers is obtained.

Penicillin a-Phenoxy-B-hydroxy-5,6-dirnethylpentyl.--

EXAMPLE I Fifty millimoles of dl-u-phenoxy-fi-hyroxypropionic acid and 200 millimoles of thionyl chloride in 50 ml. of dioxane are refluxed for 4 hours and then evaporated under reduced pressure at 3540 C. to remove excess thionyl chloride. Acetone (50 ml.) is added and the evaporation repeated. The residue is taken up in 100 ml. acetone and added dropwise to a solution of 50 millimoles of 6-aminopenicillanic acid in 250 ml. of 3% sodium bicarbonate and 100 ml. of acetone at 4 C. The pH is maintained at 7.5-8.0 by the addition of aqueous sodium hydroxide. After one hour, 100 ml. of water is added, the pH adjusted to 7.0 with aqueous phosphoric acid and the mixture extracted with an equal volume of ether. The aqueous layer is retained, adjusted to pH 2.5 with aqueous phosphoric acid and extracted twice with one volume of n-butanol. The combined n-butanol extracts are washed twice with volume of Water and then extracted with one-half volume of water, sufficient 5 N KOH being added to bring the pH to 6.5. The aqueous layer is freeze-dried to give a mixture of the potassium salts of dand l-ec-phenoxy-pl-hydroxyethylpenicillin.

In like manner, but using the appropriate acid chloride, the following new penicillins are prepared as their potassium salts.

d-a-Phenoxy-B-hydroxyethylpenicillin l-u-Phenox -,8-hydroxyethylpenicillin The d-wphenoxy-{3-hydroxypropionic acid is resolved from the dl-acid via its cinchronidine salt and purified by recrystallization from ethanol-water. The l-ot-phenoxy-B- hydroxypropionic acid is isolated via its strychnine salt followed by recrystallization from tetrahydrofuran-ether.

EXAMPLE II A solution of 0.201 g. of dl-a-phenoxy-fi-hydroxypropionic acid in 10 ml. of tetrahydrofuran and a solution of 0.204 g. l,3-dicyclohexylcarbodiimide in 5 ml. of tetrahydroluran are added simultaneously to a solution of 0.216 g. of 6-aminopenicillanic acid in 20 ml. of water: tetrahydrofuran (1:1 containing suflicient sodium bicarbonate to give a clear solution. The mixture is stirred at room temperature for 3 hours, then diluted with water, filtered to remove 1,3-dicyclohexylurea and unreacted 1,3- dicyclohexylcarbodiimide. The filtrate is extracted with a-Phenylmereapto-B-hydroxyethyl. a-Phenylmereapto-B-hydroxy-n-propyl. a-Phenylmereapto-fi-hydroxyn-butyl. a-Phenylmercapto-fi-hydroxy-npentyl. a-Phenylmereapto-B-hydroxy-n-hexyl. a-Phenylmerexpto-B-hydroxyn-heptyl. a-Phenylmercapto-B-hydroxy-E- methylpentyl. a-Phenylmereapto-fi-hydroxy-a-methylbutyl.

EXAMPLE IV The procedure of Example 11 is repeated but using nitromethane as extracting solvent in place of n-butanol. The nitromethane solution is washed with water, dried with anhydrous sodium sulfate, then titrated to pH 7 with 20% potassium hydroxide in methanol. Fifty ml. of 1:1 benzene-ethanol is added and the solution evaporated under reduced pressure until 60 ml. of distillate is collected. After one hour at room temperature, the residue is filtered to give crystalline potassium u-phenoxy-B-hydroxyethylpenicillin predominantly as the l-diastereoisomer.

EXAMPLE V Repetition of the procedure of Example TV but using methylethylketone in place of nitromethane produces a crystalline product consisting mostly of d-ot-phenoxy-B- hydroxyethylpenicillin potassium salt.

EXAMPLE V1 5 g. of dl-a-phenoxy-fl-hydroxypropionic acid is refluxed for one-half hour with 10 ml. of acetic anhydride. The excess acetic anhydride is removed under reduced pressure and the residue distilled; B.P. 165 C. at 0.4 mm.

The acetylated product is then reacted with 6-aminopenicillanic acid according to the procedure of Example II to give a mixture of the potassium salts of dand l-otphenoxy-,8-acetoxyethylpenicillin.

Repetition of this procedure using the dand l-isomers of u-phenoxy-fl-hydroxypropionic acid and of u-phenyl mercapto-B-hydroxypropionic acid with the anhydrides of acetic, propionic and butyric acids produces the respective O-acylated derivatives of dand l-a-phenoxy-B-hydroxyethylpenicillin and wphenylmercapto-B-hydroxyethylpenicillin as their potassium salts.

EXAMPLE VII 3 g. of dl-wphenoxy-{3hydroxypropionic acid is refluxed one-half hour with 5 ml. of acetyl chloride. Thionyl chloride (5 ml.) is added, the mixture refluxed for one hour then distilled in vacuo, the fraction boiling at C. at 0.35 mm. being collected.

The ot-phenoxy-B-acetoxypropionylchloride thus obtained is reacted with 6-aminopenicillanic acid according to the procedure of Example I to give a mixture of the potassium salts of dand l-ot-phenoxy-B-acetoxyethylpenicillin. The product is identical to the product of Example VI.

EXAMPLE VIII The procedure of Example V1 is repeated using the appropriate a phenoxy ,8 hydroxyalkanoic acid and ocphenylmercapto-fl-hydroxyalkanoic acid with the desired acylating agent. In this manner, the formyl, acetyl, propionyl and butyryl derivatives of the products of Example III are obtained as their potassium salts.

EXAMPLE IX The products of the preceding examples are converted to their free acid forms by neutralization of the aqueous solutions of their potassium salts with 6 N hydrochloric acid to pH 2.2. The acids are recovered by extraction into methylisobutylketone followed by evaporation of the solvent.

EXAMPLE X and the pharmaceutically acceptable salts thereof wherein X is selected from the group consisting of oxygen and sulfur; R is selected from the group consisting of hydrogen and alkyl containing 1 to 5 carbon atoms; R is selected from the group consisting of hydrogen and acyl radical of a hydrocarbon monocarboxylic acid containing 1 to 4 carbon atoms.

2. The potassium salt of d-a-phenoXy-,8-hydroxyethylpenicillin.

3. The potassium salt of l-ix-phenoxy-B-hydroxyethylpenicillin.

4. The sodium salt of l-a-phenoxy-fi-hydroxyethylpenicillin.

5. l-a-Phenoxy-B-hydroxyethylpenicillin.

6. The potassium salt of l-wplienoxy-fi-acetoxyethylpenicillin.

7. The potassium salt of l-a-phenylmercapto-fi-iydroxyethylpenicillin.

8. The potassium salt of l-ot-phenoxy-fl-hydroxy-n-propylpenicillin.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION atent No. 3, 116,285 December 31,, 1963 Walter Dv Celmer et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 49 to 57, for that portion of the formula reading read column 3 TABLE IV sixth column line 2 thereof, for 5/5" read 1/5 column 6, line 16, for "The" read For -c Signed and sealed this 16th day of June 1964 (SEAL) Attest:

ERNEST W, SWIDER EDWARD J. BRENNER Commissioner of Patents Attesting Officer 

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE STEREOISOMERS AND MIXTURES THEREOF OF COMPOUNDS REPRESENTED BY THE FORMULA: 